Moparts Tech Archive

Big Block

Hemi Head Flow #'s

lift...intake...exhaust
.100....78......65
.200...167.....138
.300...253.....195
.400...319.....241
.500...373.....275
.600...423.....281
.700...441.....293
.800...441.....293

Craig

First round of flow numbers

64hemi
Moparts Member
Posts: 553
From: Florida Panhandle
Registered: Feb 2002

I recieved the following from Tim and I left his comments in as it may be of interest to others considering FHO for your next motor and to understand what the porting process is all about.
TC

Hi Terry,
I am not quite satisfied yet, but getting real close. First stage of porting is done, and I am trying to keep the port volume as small as possible to increase the torque of your engine. It is real easy to make
huge ports to get large flow numbers, but they don't work in the real world.
Your heads are within a few percentage points of where I want to get them. I
will touch them up this week, and re-flow them. Notice that your intake will
out flow most wedge engines at only .350" - .400" lift. The stock port size
and placement does limit me somewhat, but I have achieved these type numbers
in other heads with slightly smaller valves, so I expect to get more when
they are completed. You have to sneak up on the final profiles, as there is
no going back if you remove too much port material. I still intend to limit lift
to .700", knowing that if we need more HP, the heads will be capable of flowing
the numbers at that lift. Many ports will fall off or stall out after .650-.700" lift,
and I wanted to make sure your's worked all the way up. I am always willing to
give up big top end numbers, if the port gives me great flow in the .400 to .700" range.Huge .800" numbers at the price of bad low lift numbers is a terrible trade
off. Pro-street cars need part throttle response. Once I am satisfied with
the numbers this week, then the intake goes on. We will then see if it
restricts flow in any way, and adjust as needed. Getting back to the
camshaft, I do not want to go to any more lift if possible, as valve train
life is shortened dramatically, but it is an option is HP does not come out
to were I think it should. I am putting a lot into this project (as you
are), and I expect good results. Talk to you soon, Tim

Intake
Lift CFM
.200 165
.250 214
.300 260
.350 301
.400 338
.450 366
.500 379
.550 392
.600 411
.650 423
.700 442
.750 463
.800 481.5

Exhaust
Lift CFM
.200 134 CFM
.250 157.5
.300 180.6
.350 209
.400 226.5
.450 244
.500 257
.550 268
.600 272
.650 277
.700 282
.750 283
.800 283

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